random: Add entropy test.

[sliver-openvswitch.git] / tests / test-random.c

diff --git a/tests/test-random.c b/tests/test-random.c
new file mode 100644 (file)
index 0000000..9fcc632
--- /dev/null
+++ b/tests/test-random.c
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2008, 2009, 2010 Nicira Networks.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <config.h>
+
+#include "random.h"
+
+#include <stdio.h>
+#include <string.h>
+
+int
+main(void)
+{
+    enum { N_ROUNDS = 10000 };
+    unsigned long long int total;
+    int hist16[8][16];
+    int hist2[32];
+    int i;
+
+    random_set_seed(1);
+
+    total = 0;
+    memset(hist2, 0, sizeof hist2);
+    memset(hist16, 0, sizeof hist16);
+    for (i = 0; i < N_ROUNDS; i++) {
+        uint32_t x;
+        int j;
+
+        x = random_uint32();
+
+        total += x;
+
+        for (j = 0; j < 32; j++) {
+            if (x & (1u << j)) {
+                hist2[j]++;
+            }
+        }
+
+        for (j = 0; j < 8; j++) {
+            hist16[j][(x >> (j * 4)) & 15]++;
+        }
+    }
+
+    printf("average=%08llx\n", total / N_ROUNDS);
+
+    printf("\nbit      0     1\n");
+    for (i = 0; i < 32; i++) {
+        printf("%3d %5d %5d\n", i, N_ROUNDS - hist2[i], hist2[i]);
+    }
+    printf("(expected values are %d)\n", N_ROUNDS / 2);
+
+    printf("\nnibble   0   1   2   3   4   5   6   7   8   9  10  11  12  "
+           "13  14  15\n");
+    for (i = 0; i < 8; i++) {
+        int j;
+
+        printf("%6d", i);
+        for (j = 0; j < 16; j++) {
+            printf(" %3d", hist16[i][j]);
+        }
+        printf("\n");
+    }
+    printf("(expected values are %d)\n", N_ROUNDS / 16);
+
+    return 0;
+}